1. Field of the Invention
The present invention pertains to a bulk material hauling tractor and trailer unit including bottom dump hoppers on a truck tractor and a nonsteering "pup" trailer connected to the tractor by an extended tongue to distribute bridge and roadway loading.
2. Background
In the art of truck and trailer units for hauling bulk materials several problems must be overcome in order to provide the most efficient and economical transport of material from one site to another. In the extraction and use of many types of dry bulk materials such as crushed stone, sand, coal and similar commodities, the transportation of the material becomes a significant cost factor. Moreover, the material density presents several problems to the artisan in developing the material transport vehicle. Several types of bulk material hauling vehicles have been developed including tractor and semitrailer vehicle units, combinations of tractor and double axle or wagon type trailer units and separate bulk material beds which may be mounted on conventional single axle or so called twin screw tractors.
In order to maximize vehicle payload the weight of the vehicle must be kept at a minimum while providing adequate structural integrity of the vehicle and the material containing beds or hoppers. Moreover, maximum load limits for roadways and bridges also limit the load concentration on a particular wheelbase or axle which presents a problem to the designer of the truck including tractor-trailer combinations. The synthesis of the several factors which must be considered in developing a bulk material hauling system for over-the-road as well as off road applications presents no obvious choices when taking into consideration the optimization of payload to tare weight, the compliance with roadway and bridge weight limits, and hopper design for desired loading, load containment and unloading features. However, the present invention provides a bulk material hauling system for over-the-road as well as off road use which overcomes several problems in the art.